1. Field of the Invention
The present invention relates to the preparation of a supported silver catalyst, which comprises various promoters and which is useful for the vapor phase oxidation of ethylene to ethylene oxide, by a process whereby a support is impregnated with a silver salt/amine solution as well as with various promoters and the resultant impregnated support is calcined under controlled conditions of temperature and inert atmosphere to produce the silver catalyst.
2. Description of the Prior Art
Methods are known for the preparation of supported silver catalysts useful for the vapor phase oxidation of ethylene to ethylene oxide, which methods involve impregnating a support such as alumina with a silver salt/amine solution. U.S. Pat. No. 3,702,359 is illustrative of such procedures. The preparation of silver catalysts which also contain alkali metal promoters by analogous procedures is shown, for example, in U.S. Pat. No. 3,962,136. Still further, similar procedures for the preparation of silver catalysts promoted alkali metal and rhenium and also with a co-promoter selected from sulfur, molybdenum, tungsten, chromium and mixtures are shown in U.S. Pat. No. 4,766,105.
Catalyst preparation by these prior art procedures has involved impregnating a support with the silver/amine solution which may contain the various promoters, and thereafter heating the impregnated support in a forced air oven up to a temperature of about 275.degree. C. in order to reduce the silver to metallic silver and to separate volatiles from the catalyst.
U.S. Pat. No. 5,444,034 relates to silver catalyst preparation wherein a support is impregnated with a hydrocarbon solution of a silver salt of an organic acid such as neodecanoic acid, activation in stages up to a temperature of 500.degree. C. is shown under an inert gas such as nitrogen.